ARKADELPHIA, Ark. (AP) - A 19-year-old has been arrested in connection with the killings of two girls and their stepfather in Arkadelphia, according to Arkansas State Police.

Riakos Lizana of Arkadelphia was arrested about 9:30 p.m. Saturday at a local apartment complex on a capital murder warrant in the case, state police spokesman Bill Sadler said, adding that no further information was expected to be released about the investigation prior to Lizana's first court appearance sometime this week.

"We're not going to get into any element of the investigation," Sadler told The Associated Press Sunday.

Police said the bodies were discovered Thursday evening when the mother of the girls - Anna Galbraith- arrived home that night and called police after finding her husband dead. Police said a 6-month-old girl - reported to be Bobby Galbraith's biological daughter - was found unharmed by officers who entered the home.

Sadler also declined to say whether there are other suspects in the case.

Two numbers listed for a Riakos Lizana in Arkadelphia were disconnected or no longer in service. Sadler said he did not know if Lizana had an attorney.

A suspected cause of the deaths of the three victims has not been released. Police say the bodies were sent to the Arkansas Crime Laboratory in Little Rock for autopsies.

Sadler said in a statement that special agents with the Arkansas State Police criminal investigation division had been working nonstop since Thursday on the investigation along with counterparts from the Arkadelphia Police Department and Clark County Sheriff's deputies.